A great many user interfaces for computer systems display complex information structures in graphical representations of sets of connected nodes which may be in either a hierarchical, tree-like manner, or as a graph consisting of nodes and connections. Commonly owned U.S. Pat. No. 6,816,175 relates to means and a method executable by a computer system for navigation within a tree structure with leaf nodes representing arbitrary types of objects. Today, there are many commercially available programs and program components which permit navigation of hierarchical data. For example, the JTree component which is included as part of the Java Foundation Classes (offered by Sun Microsystems of Santa Clara, Calif.) enables a programmer to display hierarchical information in a cascading tree structure. Similarly the Microsoft Foundation Classes include a tree component which is used in many applications based on the Windows Operating System including the Windows Explorer file manager included in Windows XP (distributed by Microsoft Corporation, One Microsoft Way, Redmond, Wash. 98052-6399).
In the case of trees, a style of selective display has emerged in which users selectively display and hide parts of the tree. This is particularly important when the information structures being displayed are of a considerable or even moderate size. In a technique used in the aforementioned Windows Explorer and related applications, each node in the tree may be either closed or expanded. At any one moment in time, the only parts of the tree being displayed are those that were either initially visible (when the tree was first displayed) or subsequently expanded, and that have not subsequently been closed. Further, any given node is visible at any moment in time if and only if each of its ancestors in the hierarchy is expanded at that moment.
This technique benefits the user in that it requires her to see only those portions of the information structure in which she is interested at any moment in time, thus reducing visual clutter. As her attention switches to other parts of the structure, the user may “collapse” parts that she is done with, and expand parts that merit her further attention.
This technique also offers performance advantages, since the program need only construct for display graphical elements corresponding to the nodes of the tree that the user wishes to view. For example, the tree may need only display a few hundred of the potentially hundreds of thousands of files and directories on a file system. Such a “lazy construction” of the graphical representation, and exploration of the data that is being displayed, can lead to dramatic improvements in display time.
After exploring the information structures for a while using such an interface, a user is typically left with a great many partially expanded tree branches. Although much of the tree may still be hidden, those branches that were expanded earlier can be even more distracting than if the tree were fully expanded. The very fact that these branches are expanded draws attention to them, and the user can become frustrated looking at things that are no longer of interest. Consequently the user becomes faced with the task of manually selecting and closing those things that are no longer of interest, leaving only those that are of interest.